import Text.Regex.PCRE main :: IO () main = do putStrLn ("R X" =~ "[^ ]+") putStrLn ("ℝ X" =~ "[^ ]+")

returns

R ℝ X 

The first is correct, but the second is wrong, it should only return ℝ.

I tried fixing this, and I think (but cannot confirm) that SUPPORT_UCP, SUPPORT_UTF, and perhaps also SUPPORT_PCRE8 need to be defined in pcre/config.h to ensure that pcre is compiled with unicode support. (Unfortunately, haskell complained about an unknown symbol when I tried compiling with these options, and I failed to track down the exact cause of this problem.)